As methods of analysis for detecting or quantifying an analyte in a sample with the utilization of immune response specificity, a variety of methodologies, such as immunodiffusion, enzyme assay, and agglutination, have been put to practical use. In particular, detection methods by means of flow-through assay (detection) techniques (“Guide to Diagnostic Rapid Test Device Components,” 2nd edition, published by Scheicher & Schuell company, January 2000, Edited by Lisa Vickers, pp. 6-8 and JP Patent Publication (Kokoku) No. 7-34016B (1995)) or by means of immunochromatography assay (detection) techniques (a lateral-flow assay, a tangential-flow assay, JP Patent Publication (Kokoku) No. 7-13640B (1995), JP Patent No. 2890384) spread rapidly because of the convenience thereof in recent years. The principles of such detection methods are briefly described below. According to many of commercial flow-through assay techniques, a capture reagent (e.g., antibody) for capturing an analyte (e.g., antigens) is first immobilized on a membrane (a solid-phase support), and a given amount of a sample comprising an analyte-containing specimen suspended therein is supplied to the membrane. When the sample passes through the membrane, the existing analyte is captured by a capture reagent that has been immobilized on the membrane, and a complex of the analyte and the capture reagent is then formed. Subsequently, a given amount of a labeled reagent containing a ligand that specifically binds to the analyte (e.g., enzyme labels for the analyte) is supplied, and a complex of the capture reagent, the analyte, and the labeled reagent is formed at a site at which the capture reagent has been immobilized. The labeled reagent can be detected by any technique (in the case of an enzyme label, a color reaction takes place with the supply of a substrate) to determine the presence of the analyte.
Many types of commercial kits for immunochromatography assay techniques each comprise a strip membrane. The membrane comprises a capture reagent (e.g., antibody) for capturing an analyte (e.g., antigens) immobilized at one of its ends in the lengthwise direction, and a labeled reagent (e.g., colloidal gold particles that can be visualized) comprising a ligand that specifically binds to the analyte sustained in a spreadable manner on the membrane at the other end. If a given amount of a sample comprising an analyte-containing specimen suspended therein is supplied to the side of the membrane that sustains the labeled reagent, the analyte binds to the labeled reagent to form a complex of the analyte and the labeled reagent when the sample is spread over the membrane. The complex of the analyte and the labeled reagent spreads and flows over the membrane, and it is captured by the capture reagents immobilized on the membrane. Thus, a complex of the capture reagent, the analyte, and the labeled reagent is formed at a site at which the capture reagent has been immobilized. The presence of the analyte can be determined by detecting the labeled reagent by any technique (in the case of colloidal gold particles that can be visualized, an image of the aggregate thereof is to be detected).
In the many assay techniques, since large quantities of impurities were contained in analyte-containing specimens, a variety of types of chemical or physical preparations are carried out in order to remove the impurities. From such prepared samples, impurities are removed as much as possible, and the analyte is then extracted therefrom to form a complex of the capture reagent, the analyte, and the labeled reagent. This is an essential condition for an assay technique having high sensitivity and specificity. However, the procedures therefore are laborious and time consuming, which result in decreased operational efficiency. When an assay technique requires laboriousness, it often causes operational errors. This deteriorates the quality of the assay technique in terms of safety, costs, and operational efficiency.
Patent Document 1: JP Patent Publication (Kokoku) No. 7-34016B (1995)
Patent Document 2: JP Patent Publication (Kokoku) No. 7-13640B (1995)
Patent Document 3: JP Patent No. 2,890,384
Non-Patent Document 1: Guide to Diagnostic Rapid Test Device Components, 2nd edition, published by Scheicher & Schuell company, January 2000, Edited by Lisa Vickers, pp. 6-8